Hardness of water is caused by the presence of ______ salts.

Appeared in: Raj. CHO - 2023

Explanation

Water hardness is defined by its 'soap destroying power' and is caused by dissolved mineral ions that react with soap to form scum.
The primary ions responsible for water hardness are divalent cations, mainly calcium (Ca²⁺) and magnesium (Mg²⁺).
These ions are typically present as bicarbonates, sulfates, chlorides, and nitrates.
Among the given options, only magnesium is a principal cause of water hardness.

Option A: Chlorine is a halogen used for water disinfection to kill pathogens. It does not contribute to water hardness.
Option B: Boron is a trace element and is not present in sufficient quantities to be considered a cause of water hardness.
Option D: Potassium salts are very soluble in water and do not precipitate with soap. Therefore, they do not cause hardness.

Visual 1: Diagram - A simple diagram comparing two beakers. One with soft water showing abundant lather with soap, and another with hard water showing scum formation and no lather. This visually explains the primary effect of hardness.
Visual 2: Flowchart - A flowchart illustrating the classification of water hardness into 'Temporary' and 'Permanent', listing the specific salts for each and the methods for removal (e.g., Boiling for temporary, Ion Exchange for permanent).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Causes of Water Hardness as background academic context rather than a clinical decision trigger.
In healthcare settings, hard water can cause mineral deposits (scale) to build up in autoclaves, sterilizers, and water heaters, reducing their efficiency and lifespan.
Washing hands frequently with hard water can contribute to skin dryness and irritation (contact dermatitis), which is a concern for healthcare workers.
What if? - If a hospital's sterile processing department reports significant scaling on its equipment, the immediate suspicion should be high permanent hardness in the water supply, requiring investigation and likely installation of a water softening system (like an ion exchanger).

How to Approach the Question

This is a factual recall question from environmental health and chemistry.
First, identify the core concept in the question stem: 'Hardness of water'.
Recall the definition of water hardness, which relates to its reaction with soap.
Access your knowledge about the specific chemical ions that cause this phenomenon. The most common ones are calcium and magnesium.
Scan the options to see if either calcium or magnesium is listed.
Select the option that matches your recalled knowledge. In this case, 'Magnesium' is present.

Concept Tested & Keywords

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Practise the full Raj. CHO - 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.